A potent mix of rising exports, consumer spending and business investment helped the U.S. economy end the year on solid footing.

Gross domestic product, the broadest measure of goods and services churned out by the economy, grew at a seasonally adjusted annual rate of 3.2% in the fourth quarter, the Commerce Department said. That was less than the third quarter's 4.1% pace, but overall the final six months of the year delivered the...